Yieldable clutching means



June 14, 1938; J, WOHLFELD 2,120,384

YIELDABLE CLUTCHING MEANS Filed May 23, 1954 I [WEN mg gbg s- 4TTORNE YPatented June 14, 1938 YIELDABLE CLUTCHING MEANS Jacob Wohlfeld,Detroit, Mich, assignor to George Lovequest, Detroit, Mich.

Application May 23, 1934, Serial No. 727,136

'20 Claims.

The invention relates to yieldable clutching means for valve operatingmechanism and other motion transmitting systems.

An object of the invention is to provide yield.-

5 able clutching means of durable, compact, and

inexpensive construction suitable for use in various motion transmittingsystems, as in the valve operating mechanism of an internal'combustionengine to minimize noise and play and to auto- -matically compensate forvariations in the length of the valve caused by temperature changes andwear, the clutching means being capable of mounting in a self-containedtappet permitting replacement'of a tappet of conventional type.

- Another object of the invention is to provide a yieldable clutchingdevice having spring-urged friction means through which the operatingpressure is transmitted, and a more specific object is to form thefriction means by a confined plug of plastic or deformable material.

The invention .further consists in the several features hereinafterdescribed and claimed.

In the accompanying drawing,

Fig. l is a sectional elevation of a valve operating mechanism equippedwith a slack adjuster having yieldable clutching means embodying theinvention, and

Fig. 2 is a detail view of some of the slack adjuster parts.

In the drawing, l designates the cylinder block of an internalcombustion engine provided with the usual poppet valve ll engageablewith a valve seat 12 and having its stem l3 slidably mounted in theblock and urged to valve-closing position by the usual surrounding valvespring M bearing on a valve washer, l5 held on the stem by a. retainer16. A tappet member I1 is slidably mounted in the cylinder block belowand in axial allgnment'with the valve stem and has the usual enlargedlower end l8 periodically lifted by a cam IS on a cam shaft 20 tothereby actuate the valve.

It will be obvious that for the type of valve operated through a rockerarm, the valve stem 13 is replaced by the usual valve rod or push rodwhich may also be regarded as a valve stem.

The tappet member ll, instead of having the usual adjusting screw means,is provided with the. yieldable clutching means of the invention. Thetappet -member forms a cylinder into the upper end of which is forced atubular plunger body 2| having an annular flange 22 at its upper andengaging the upper face of the tappet member. A coiled spring 23 ishoused within the tap- '55 pet member below the plunger body and bearsat its upper end on a disk-like spring seat member I 24 limited in itsupward movement by the lower end of the plunger body. A relief opening25 is drilled into the lower portion of the tappet member.

The plunger body 2| has formed therein aligned upper and lower bores 26and 21, respectively, communicating with an intermediate upwardlydiverging conical bore 28, the upper bore 26 being of larger diameterthan the lower bore 7 21. An-upper plunger 29 is slidably mounted in thebore 26 and projects upward from the plunger body to engage the lowerend of the valve stem l3. A lower plunger 30 is slidably mounted in thebore 21 and has a projecting conical lower end engageable with the upperface of the spring seat member 24, a recess 3! being formed in this faceto receive the conical end. Between the plungers 29 and 30 isinterposeda compact, substantially voidless plug or briquet 32 .of soft, plasticor deformable coherent material, such as graphite, although in someinstances lead, a plastic amalgam, or rubber can be used.

. Fine powders, such as of carbon or metals, for instance, aluminum, arealso usable. If desired, graphite may be mixed with the powders. Theplug of solid but flowable material is confined by the plungers in theconical bore 28 which it. frictionally engages, and under pressure fillsthe entire space between the adjacent end faces of the plungers, theflowablematerial and the plug or mass formed thereby being substantiallyincompressible. The space within the conical bore forms what may betermed an extrusion chamber for the deformable plug. While the bores 26and -35 21 and the plungers therein are here shown to .be of circularcross-section, it will be obvious that other cross-sections may be used.

Before the tappet assembly is installed in the engine, the free overalllength of the assembly is slightly greater, say 0.015 inch, than thenormal distance between the cam and lower endof thevalve stem, and thespring 23 forces the spring seat member 24 into abutment with the lowerend of the plunger body 2|. When the tappet assembly is installed, theplunger 29 engaging the lower end of the valve stem graduallymovesdownward under urge of the valve spring until the valve engages itsseat and a small clearance, say 0.030 inch, exists between the. springseat member and the bottom face of the plunger member, it being notedthat the smaller plunger 30 movesfarther than the larger plunger 29.During this movement of the plungers, the interposed plug 32 lengthensand changes its shape,

unchanged. The deformable material presents a smooth surface which is insubstantially continuoils or unbroken slidable contactwith thewalls ofthe chamber..

In operation, the valve is periodically actuated by the rotating camshaft, the tappet member forming a motion-transmitting compressionmember. In the interval during which the valve is closed, the pressureof the tappet spring 23 acting upward through the valve seat member 24,the lower plunger 30, the plastic or flowable material 32, and the upperplunger 29, tends to increase the length of the tappet. This pressure isopposed by the somewhat greater valve spring pressure with the resultthat the tappet completely fills the space between the cam and the lowerend of the valve stem, but does not lift the valve off its seat.

When the cam l9 lifts the tappet member H, the upper plunger 29 liftsthe valve from its seat. During this movement, the force acting downwardthrough the valve stem 13 is transmitted through the upper plunger 29which in turn transmits it to the plastic or flowable material formingthe plug 32. Some of this force. is used in overcoming the frictioncaused by moving the plastic material downward in the conical bore 28 ofthe plunger body 2| and in changing the shape of the plug, the balanceof the force being transmitted to the smaller lower plunger 30 which inturn transmits it to the spring seat member 24,

then to the spring 23 and to the bottom portion of the tappet memberl'l. During the interval from valve opening to maximum valve velocityupward, the valve spring pressure plus the force due to the inertia ofthe valve, valve spring, washer, retainer and upper plunger tend toshorten the tappet, while the tappet spring and friction of the flowablematerial oppose this total force. During the interval from maximum valvevelocity upward to maximum valve velocity downward, the valve springpressure minus the force due to the inertia of the valve, valve spring,washer, retainer and upper plunger and plus the force due to the inertiaof the tappet assembly (lessupper plunger) tend to shorten the tappet,and the tappet spring and friction of the flowable material oppose thistotal force. During the interval from maximum valve velocity downward tovalve closing, the forces acting are the same as those in the intervalfrom valve opening to maximum valve velocity upward. The forces due tothe inertia of the tappet spring seat member 24, lower plunger 30 andflowable material, although small, are added to the tappet springpressure for the interval from maximum valve velocity upward to maximumvalve velocity downward, and are subtracted from tappet spring pressurefor the interval from valve opening to maximum valve velocity upward,and for the interval from maximum valve velocity downward to valveclosing. By varying the tappet spring pressure, the relative areas ofthe upper and lower plungers, the friction or fiowability of the plasticmaterial, and the shapeof the space through which the plastic materialmoves, to suit any particular valve meehanisir'i'i'it is possible tomaintain a tappet assembly length that will fill the space between thecam and the lower end of the valve stem, with a positive seating of thevalve and full valve lift, except for a very slight shortening duringthe valve-open period, say considerably less than 0.001 inch.

If the valve stem lengthens incident to an in- I Letters Patent is.

crease in temperature and the valve tends to ride, the upper plunger 29gradually moves downward until the valve fully seats and a clearance of,say, 0.038 inch exists between the spring seat member 24 and the lowerend of the plunger body 2|.

The pressure or force acting on the upper plunger 29 is transmitted tothe lower plunger 30 through the plastic or flowable material whichfunctions like a plastic metal, has a comparatively slow action, and canbe confined under the operating pressures without appreciable loss. Theplastic or. flowable material thus exerts a damping efiect. When theplunger 29 moves downward, the flowable material is extruded from thelargerplunger bore. 26 to the small plunger bore 2| and the smallerplunger 30 moves downward a greater distance than the upper plunger.When the lower plunger moves upward, the flowable material is liftedrelatively freely as a briquet away from the tapered walls of itschamber, and the upper plunger moves with the flowable material untilthe upper plunger abuts against the valve stem and stops. The lowerplunger continues to move until the flowable material changing formentirely fills the con-I fining space. Obviously, the force applied tothe smaller plunger necessary to move the larger plunger is less thanthat applied to the larger plunger in order to move the smaller plunger,considering the plunger body assembly as a unit consisting of the parts2|, 29, 30, and 32.

In general, the tappet assembly herein described will automatically,when in action, increase or decrease in overall length to suit thevariations in distance between the cam. and the end of the valve stem,so that the valve will seat vention is here shown to be embodied in aslack adjuster for a valve-operating mechanism, it is also applicable toother motion-transmitting systems wherein it is desired to minimize lostI motion, to compensate for variations incident to temperature changesand other causes, and to permit motion in one direction more freely thanin the opposite direction. Among such systems are brake systems, shockabsorbers, door checks,

remote control mechanisms, jacks ..too1 fixture locks, and the like.

What I claim new and desiregio secure by 1. The'combination of a bodyhaving bores and a chamber between and communicating with said bores,plungers in said bores, a compact, substantially voidless mass of soft,solid but flowable material confined in said chamber by said amass-iplungers in said bores, a mass of flowable material of high internalfriction confined in said chamber by said plungers and engaging thewalls of said chamber, and yielding means for applying pressure to saidmaterial through the smaller plunger.

3.- The combination of a motion-transmitting member having a pair ofbores extending in the direction of motion, there being a chamberbetween and communicating with said b0res,,

plungers in said bores, a compact, substantially voidless mass of soft,solid but flowable material in said chambenfrictionally engaging thewalls of said chamber, and spring means in said member for applyingpressure to said material through one of said plungers.

4. The combination of a tubular member having a pair of axially spacedbores adjacent one end extending longitudinally of said member, theouterbore being of larger diameter than the inner bore and there being acommunicating chamber between said bores, plungers slidable in saidbores, a mass of solid but flowable material confined in said chamber bysaid plungers and frictionally engaging the walls of said chamber,spring means in said tubularmember for applying pressure to saidmaterial through the, smaller plunger, and stop means for limiting themovement of said spring means.-

6. A slack adjusting tappet comprising a movable tubular member, aplunger body secured in one end of said member and having bores atopposite ends extending longitudinally of said "member, there being achamber between and communicating with said bores, plungers slidable insaid bores, a mass of solid but fiowable material confined in saidchamber by said plungers and frictionally engaging the walls of saidchamber, and spring means in said tubular member for applying pressureto said material through the plunger at the inner end of said plungerbody. 7. Yieldable clutching means comprising a pair of relativelymovable members, friction means for resisting relative movement of saidmembers in'cluding a compressed but flowable mass of graphite, andyielding means for applying pressure to said friction means and tendingto move one member with respect to the other.

8. Yieldable clutching means comprising a pair of relatively movablemembers, friction means for resisting relative movement of said membersineluding a compressed but fiowable mass of powdered material, andyielding means for applying pressure to said friction means and tendingto move one member with respect to the other.

9. Yieldable clutching means com'prisinga pair of relatively movablemembers, friction means for resisting relative movement of said membersincluding a compressed but fiowable mass of powdered metal, and yieldingmeans for applying pressure to said friction means and tending to moveone member with respect to the other.

10. Yieldable clutching means comprising a pair of relatively movablemembers, friction means for resistingrelative movement of said membersincluding a compressed but flowable mass of plastic metal, and yieldingmeans for applying pressure to said friction means and tending to moveone member with respect to the other.

11.Yieldable clutching means comprising a pair of relatively movablemembers, friction means for resisting relative movement of said membersincluding a compressed but i'lowable mass of powdered carbon, 'andyielding means for applying pressure to said friction means and tendingto move one member with respect to the other. I

12. Yieldable clutching means comprising a pair of relatively movablemembers, friction 'means for resisting relative movement of said membersincluding a compressed but fiowable mass of graphite bearing material,and yielding means for applying pressure to said friction means andtending to move one member with respect to the other.

13. The combination of a body having a cham-' ber with walls, membersmovable in said body and communicating with said chamber, and a compact,substantially voidless mass of soft, solid but flowable frictionmaterial in said chamber for transmitting pressure between said members.and deformable by movement along said walls to retard relative movement.

14. The combination of a body having a chamber with converging walls,plungers movable in said body and communicating with said chamber, and amass of solid but flowable material in said chamber for transmittingpressure between said plungers and deformable by movement along saidconverging walls to retard relative movement.

15. The combination of a body having a chamber with converging walls, amember relatively movable in said body and ,communicating with saidchamber, and a mass of solid but. flowable friction material in saidchamber engageable with said m mber and deformable by movement alongsaid converging walls to retard relative movement of said body andmember.

16. The combination of a pair of relatively movable members, andfriction clutching means for resisting relative movement of said membersand comprising a compact, substantially voidless mass of soft, solid butflowable friction material. said material being substantiallyincompressible and having a smooth deformable surface in substantiallycontinuous frictional contact with the surfaces of said members.

17. The combination of a body having a pair of guide'openings ofdifferent cross-sectional area and a chamber at-the inner ends of saidopenings, members slidably fitting in said guide openings and formingthe opposite'ends of said chamber, and'a dense mass of soft, solid butiiowable material confined in said chamber by said members and having aclutching engagement with the walls of said chamber, said chamber beinglarger at the end defined by the larger guide opening to permitrelatively easier movement of said material toward said end than towardthe smaller end, and means acting through the smaller member toapplypressure to said material in a direction tending to effect the freemovement of said material.

18. Yieldable clutching means comprising a pair of relatively movablemembers, friction means for resisting relative movement of said prisinga confined mass of compact, soft, solid but 10 flowable graphite.-

20. The combination of relatively movable interfitting members forming achamber, and friction clutching means for resisting relative movement ofsaid members comprising a dense, substantially incompressible,briquet-like' mass of soft, solid but iiowable coherent material con-'fined in and filling said chamber and having a friction clutchingengagement with walls of said chamber.

JACOB womr'mln. 10

